Panel 1: find Elly and Phil at the baggage-smashing machine thought-bubbling 'grumble' and 'snarl' at each other like kids fighting over a toy.
Panel 2: They continue this at the generic car rental office.
Panel 3: When they get to the old place, they get greeted by their parents.
Panel 4: We get a stupid person's idea of irony when Marian gets all gushy about how they're acting like brother and sister again.
Summary: What we have here is what happens when what goes without saying isn't said. Marian never knows that the pump organ is a symbol for who is Best And Most Beloved Child and she never knows about the bad feelings it inspires.